A couple of points..it may not be useful to translate sakkya-ditthi as "ego".There is a risk of confusion with western psychoanalytic models.Secondly it might be useful to think of sakkya-ditthi not as a noun , not as a thing, but as a verb..an action. Specifically as an act of identification with the kandhas/skandhas.

Śūnyatā wrote:In your own words, how would you define "the ego" (sakkaya-ditthi)?

Gratefully yours,Śūnyatā

A combination of parts mistaken for something they are not.

This offering maybe right, or wrong, but it is one, the other, both, or neither!Blog,-Some Suttas Translated,Ajahn Chah."Others will misconstrue reality due to their personal perspectives, doggedly holding onto and not easily discarding them; We shall not misconstrue reality due to our own personal perspectives, nor doggedly holding onto them, but will discard them easily. This effacement shall be done."

I tend to view our ego or sense of self as the product of a mental process that arises due to the presence of clinging (upadana) in the mind with regard to the five aggregates, a process that acts as a condition for the birth (jati) of the conceit 'I am,' the self-identification that designates a being (satta).